A typical endoscope comprises a cylindrical stainless steel case enclosing a bundle of fiber optic wires which transmit light from a distal end (tip end) to a proximal end of the endoscope. A fiber optic cable delivers light from a light source into the case through an aperture situated near the proximal end of the endoscope. The fiber optic wires transmit the light through to the distal end, where the light exits the endoscope and illuminates the area near the distal end. The endoscope in turn transmits an image of that area through the fiber optic wires to an eyepiece lens at the proximal end. A video camera coupled to the eyepiece converts the image into electronic signals and transmits the signals to a video monitor, where the image is displayed.
Endoscopes are used most often in "minimally invasive surgery", in which an endoscope is inserted into a patient, allowing a surgeon to illuminate and view the interior of the patient with minimal penetration. The use of endoscopic surgery is growing, in large part because it is generally safer and less expensive than conventional surgery, and patients tend to require less time in a hospital after endoscopic surgery. As endoscopic surgery becomes more common, there is an increasing need to accurately evaluate the performance characteristics of endoscopes.
To accurately test the optical performance of an endoscope, both the lens and the fiber optic wires should be evaluated. For example, some fiber optic wires may be damaged and only partially transmit light. In addition, the lens may distort images or blur the sharpness of image colors. These and other shortcomings in the optical performance of endoscopes may be the result of imperfections in the manufacturing process and/or may develop as the endoscope is used over time.
A further complication is that endoscopes vary in length, diameter and tip angle, which is the angle between the direction of view of the longitudinal axis of the endoscope. A system for evaluating endoscope performance ideally would be able to test and evaluate the performance characteristics of both the lens and fiber optic wires of an endoscope, and have the further capability of accommodating endoscopes having varying physical characteristics.